Reduced current charge pump

1. A charge pump comprising:

a flying capacitor configured to be switched between at least two states, wherein the flying capacitor is configured to provide the output voltage from an input voltage;

a plurality of switching devices coupled in parallel between the input voltage and the flying capacitor, the plurality of switching devices configured to selectively provide a variable available drive current to the flying capacitor;

a first comparator configured to compare the output voltage to a first reference voltage and to provide a first feedback signal using the comparison;

a second comparator configured to compare the output voltage to a second reference voltage and to provide a second feedback signal using the comparison;

a logic circuit configured to select at least one of the plurality of switching devices to provide the variable available drive current to the flying capacitor, wherein the logic circuit selects the at least one of the plurality of switching devices using the first and second feedback signals from the first and second comparators, wherein the variable available drive current is configured to vary depending on the selected at least one of the plurality of switching devices; and

wherein the plurality of switching devices include binary devices having an ON state and an OFF state, the binary devices configured to provide a discrete magnitude of available drive current in the ON state and an insignificant magnitude of available drive current in the OFF state.

2. The charge pump of claim 1 , wherein the plurality of switching devices include a first switching device configured to provide a first available drive current and a second switching device configured to provide a second available drive current, wherein the first available drive current substantially corresponds to the second available drive current.

3. The charge pump of claim 2 , wherein the logic circuit is configured to increase the number of the selected at least one of the plurality of switching devices to increase the variable available drive current.

4. The charge pump of claim 2 , wherein the logic circuit is configured to decrease the number of the selected at least one of the plurality of switching devices to decrease the variable available drive current.

5. The charge pump of claim 1 , wherein the plurality of switching devices include a first switching device configured to provide a first available drive current and a second switching device configured to provide a second available drive current, wherein the first available drive current is greater than the second available drive current.

6. The charge pump of claim 5 , wherein the logic circuit is configured to increase the available drive current by selecting the first switching device to provide the variable available drive current instead of the second switching device.

7. The charge pump of claim 1 , wherein the first reference voltage and the second reference voltage include bounds for the output voltage and the first reference voltage is higher than the second reference voltage;

wherein the first comparator is configured to provide a high signal when the output voltage is above the first reference voltage; and

wherein the logic circuit is configured to change the selected at least one of the plurality of switching devices to decrease the available drive current in response to the high signal.

8. The charge pump of claim 1 , wherein the logic circuit is configured to provide a plurality of control signals configured to select at least one of the plurality of switching devices using the first and second feedback signals.

9. The charge pump of claim 1 , wherein the first comparator is configured to provide a high signal when the output voltage is above the first reference voltage and to provide a low signal when the output voltage is below the second reference voltage; and

wherein the second comparator is configured to provide a high signal when the output voltage is below the second reference voltage and to provide a low signal when the output voltage is above the second reference voltage.

10. A method for providing an output voltage from a flying capacitor, the method comprising:

receiving an input voltage at a plurality of switching devices;

providing a variable available drive current to the flying capacitor using at least one of the plurality of switching devices;

providing the output voltage with the flying capacitor;

comparing the output voltage with at least one reference voltage;

providing at least one feedback signal using the comparison; and

selecting the at least one of the plurality of switching devices using the feedback signal, wherein the variable available drive current varies depending on the selected at least one of the plurality of switching devices;

wherein the selecting the at least one of the plurality of switching devices includes increasing the available drive current when the output voltage is below the second reference voltage; and

wherein the providing the output voltage using the at least one of the plurality of switching devices includes using a binary weighted current source, and wherein the increasing the available drive current includes increasing the number of switching devices used to provide the output voltage.

11. The method of claim 10 , wherein the comparing the output voltage to at least one reference voltage includes:

comparing the output voltage to a first reference voltage and providing a first feedback signal using the comparison to the first reference voltage; and

comparing the output voltage to a second reference voltage and providing a second feedback signal using the comparison to the second reference voltage, the second reference voltage lower than the first reference voltage.

12. The method of claim 10 , wherein the selecting the plurality of switching devices includes decreasing the available drive current when the output voltage is above the first reference voltage.

13. The method of claim 10 , wherein the providing the feedback signal includes providing a high signal from a comparator when the output voltage is above the at least one threshold and providing a low signal from a comparator when the output voltage is below the at least one threshold.

14. A circuit for providing an output voltage, the circuit comprising:

a flying capacitor configured to be coupled between at least two states, wherein the flying capacitor is configured to provide the output voltage from an input voltage;

a binary weighted current source including a plurality of switching devices coupled in parallel between the input voltage and the flying capacitor, the plurality of switching devices configured to provide charge from the input voltage to the flying capacitor, wherein at least one of the plurality of switching devices is configurable into an ON state and OFF state such that differing current is available to be provided to the flying capacitor depending on whether the at least one switching device is in the ON state or OFF state;

a first comparator configured to compare the output voltage to a first reference voltage and provide a first feedback signal using the output voltage, wherein the first reference voltage includes a desired output voltage;

a second comparator configured to compare the output voltage to a second reference voltage and provide a second feedback signal using the output voltage, wherein the second reference voltage includes a high output voltage threshold;

a third comparator configured to compare the output voltage to a third reference voltage and provide a third feedback signal using the output voltage, wherein the third reference voltage includes a low output voltage threshold; and

a logic circuit configured to select at least one of the plurality of switching devices to provide the input voltage to the flying capacitor using the feedback signal from the first, second, and third comparators.

15. The circuit of claim 14 , wherein the logic circuit is configured to hold the selected at least one of the plurality of switching devices to provide the available drive current when the first feedback signal indicates that the output voltage is near the desired output voltage.

16. The circuit of claim 14 , wherein the logic circuit is configured to increase the number of the selected at least one of the plurality of switching devices to increase the available drive current when the second feedback signal indicates that the output voltage is above the high output voltage threshold.

17. The circuit of claim 14 , wherein the logic circuit is configured to decrease the number of the selected at least one of the plurality of switching devices to decrease the available drive current when the second feedback signal indicates that the output voltage is below the low output voltage threshold.

18. A charge pump comprising:

a flying capacitor configured to be switched between at least two states, wherein the flying capacitor is configured to provide the output voltage from an input voltage;

a plurality of switching devices coupled in parallel between the input voltage and the flying capacitor, the plurality of switching devices configured to selectively provide a variable available drive current to the flying capacitor;

a first comparator configured to compare the output voltage to a first reference voltage and to provide a first feedback signal using the comparison;

a second comparator configured to compare the output voltage to a second reference voltage and to provide a second feedback signal using the comparison;

a logic circuit configured to select at least one of the plurality of switching devices to provide the variable available drive current to the flying capacitor, wherein the logic circuit selects the at least one of the plurality of switching devices using the first and second feedback signals from the first and second comparators, wherein the variable available drive current is configured to vary depending on the selected at least one of the plurality of switching devices;

wherein the first reference voltage and the second reference voltage include bounds for the output voltage and the first reference voltage is higher than the second reference voltage;

wherein the first comparator is configured to provide a high signal when the output voltage is above the first reference voltage; and

wherein the logic circuit is configured to change the selected at least one of the plurality of switching devices to decrease the available drive current in response to the high signal.

19. The charge pump of claim 18 , wherein the plurality of switching devices include a first switching device configured to provide a first available drive current and a second switching device configured to provide a second available drive current, wherein the first available drive current substantially corresponds to the second available drive current.

20. The charge pump of claim 18 , wherein the plurality of switching devices include a first switching device configured to provide a first available drive current and a second switching device configured to provide a second available drive current, wherein the first available drive current is greater than the second available drive current.